Back in the day I was one of those serious MA guys. I studied things that most people have never heard of and would crap themselves if they saw it. One of the things that most of the 'Hard' MA's people either don't know or won't tell you is that you MUST stay in training. 'Iron Hand' or 'Iron Body' training is probably the biggest example of this. I have seen people that will pound their fists in stacks of steel plates 1000 times a day, have people beat their bodies with bamboo sticks for an hour, all kinds of stuff. The bones and joints of these people are like iron, analysis of their bodies show 7x the bone density of the average human. I myself use to do a version of this (a considerably less punishing version) until I received a near crippling injury (a crippling one in terms of my training) and had to stop training pretty much completely for about 5 years. The result was arthritis in my hands, knees, back and elsewhere. You see all that pounding stimulates bone growth, while also preventing the build-up of calcium in the joints, this makes your bones hard and dense, but if you stop the pounding the bone growth continues and the destruction of the growth in the joints ceases. What all this means is that a significant portion of the 'Hard Arts' are going to be very hard on your body and failure to stay in training is going to result in problems later on. Don't go down this road unless you are willing to make a lifetime commitment, as in marriage a divorce is going to be painful.
As to the "Mystical" aspect of MA, much of this is a problem of translation as many of the concepts involved have literally no counterpart in Western philosophy. One of the best examples of this is the Zen concept of 'No-Mind". "No-Mind" is a literal translation of the Japanese term and it has been understood by many in the west (Ayn Rand was especially guilty of this) as meaning the 'absence of thought' or a failure to use the mind and depending on some mystical 'thing' to replace it. However, in the late 20th century Robert Anton Wilson and others began talking about "Internal Dialog'. Internal dialog is simply that voice in your head that you hear all the time, you talking to yourself. People do this all the time, you brain is constantly going "Did I shut off the lights?", "Is this idiot ever going to shut up?" "If he does this I should do that" and on and on. Even as you read this you are thinking about examples for and against my thesis or composing your reply or whatever. The greater part of Zen meditation is devoted to simply turning off this voice, of quieting the internal dialog, but because it uses flowery words such as "The mind like water" and such it becomes confusing to the analytical, materialistic (i.e. physical world) western mind. If the Zen concept had simply said "Quiet that yammering voice in your head" we would have understood it. When a Zen parable tells us "When eating, eat" we don't understand it, but if it said "When eating, don't think about anything else, don't even think about moving the fork to your mouth" it would have gone better. Mantras are even worse for Westerners because people mistake them for prayers because it seems a lot like reciting 'Hail Mary's', when in truth the purpose of the mantra is simply designed to drown out the internal dialog, to give your brain something to occupy itself with rather than letting it get distracted. In truth most shooters have been trained in a concept very much like "No-Mind", we call it muscle memory training, or conditioned reflex, we train to do things like drawing or reloading without thinking about it, in Zen it is called "action without thought". Of course, too many Western and even Eastern trainers wind up making these things MORE mystical and pseudo-religious because they themselves cannot translate the concepts properly. So don't get too bent out of shape about such things unless it really detracts from the physical aspects of your training.
As far as what to train in, I recommend what is now called "American Combatives", which is simply the old WWII style hand-to-hand combat, especially that developed by the OSS and taught by Rex Applegate. In fact, if you cannot find training in this locally, get a few friends together, buy a copy of "Kill or Get Killed" and Practice what it teaches and you will find yourself fully capable of handling probably 75% of the situations you are likely to face. In fact Krav Maga in nothing more than the old Fairbairn/Applegate system tarted up with a bunch of borrowed stuff, mostly from Tae Kwon Do, which (IMHO) makes it harder to train in (especially for the more mature and out of shape among us) and less useful overall. Sambo is even worse because of the emphasis on hard grappling (many instructors here are into Combat or Special Sambo which is a harder version big on grappling and striking). Judo and Jujitsu are ok, if you can put up with the physical requirements, and Tai Chi Chuan is actually an awesome form of martial art, IF you get a good instructor who understands it's martial aspect and you have 5 or 10 years to get good (I do recommend it as a style to practice just for it's health benefits and it DOES have them). I wouldn't recommend much else right now for anyone who doesn't plan to devote years to training.
If I had my life to do over I would have gotten into JKD and Silat, but I don't. Just remember, if you urinate in Jet Li's cornflakes you are gonna' catch an ass-whoopin', don't think a couple days a week at Master Kwan's McDojo is going to change that. Keep your goals realistic, use what has been proven to work in the street and on the battlefield (i.e. "American Combatives" or The Fairbairn/Applegate system) for the last almost 70 years and you will handle the majority of problems which can be handled by empty-hand fighting. Remember too, the first thing to fight with is your brain, mostly by recognizing and AVOIDING a fight. I've been called a coward (and similar, less polite things) more than my grand kids have been called to dinner and it never hurt as much as one ass-whoopin' would have.